Extraction of hydrocarbon oils



Sept. 11, 1956 J. I. SLAUGHTER ETAL 2,762,750

EXTRACTION OF HYDROCARBON 0114s Filed April 27,. 1955 2 Sheets-Sheet 1 "E Q 'S 5 Q m k E, 8 N 5 R 40 a0 k a 3 5 a i o o o /00 200 300 400 500 500 PART/AL PRESSURE BF psl'g.

Jo/m Slaughter David A. McCall/0y Arthur I. Lien W a (W- ATTOR/VEY Sept. 11, 1956' Filed April 27, 1955 J- l. SLAUGHTER ET AL EXTRACTION 0F HYDROCARBON OILS.

2 Sheets-Sheet 2 United States Patent EXTRACTION OF HYDROCARBON OILS John I. Slaughter, Whiting, Ind., David A. Mc'Caulay, Chicago, Ill., and Arthur P. Lien, Highland, and Carl E. Johnson, Grifith, Ind., assign'ors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application April 27, 1955, Serial No. 504,172 Claims. (Cl. 196-13) This invention relates to the extraction of hydrocarbon oils and in particular it concerns the treatment of hydrocarbon oils with phosphoric acid and BFs as the selective solvent.

Hydrocarbon oils such as petroleum and the various fractions thereof, coal tar distillates, shale oils and the like are generally comprised of a mixture of difierent types of compounds. phatic, and alicyclic hydrocarbons as well as sulfur compounds, nitrogen compounds and the like. It is frequently desirable that hydrocarbon fractions be produced free from one or more of several types of these compounds. The petroleum refiner generally desires to remove sulfur compounds from petroleum or the various fractions thereof, such :as gasoline, kerosene, burning oils, etc. The presence of aromatic hydrocarbons in kerosene causes the latter to burn with a'smoky flame and removal of the aromatic hydrocarbons is often necessary. Condensed ring aromatics lower the viscosity index of lubricating oil stocks and consequently their removal from such a stock is highly desired. The quality of various other petroleum fractions available to the refiner should They may contain aromatic, alisimilarly be refined to remove undesired components such as the aromatic hydrocarbons, sulfur compounds and the like.

Hydrocarbon oils frequently contain components such as polyalkyl benzenes and polynuclear aromatics whose recovery may be desirable. The separation of polyalkyl 1 1 benzenes and polynuclear aromatics in high purity has become more important in recent years because of the growing demand for particular aromatic hydrocarbons for use in the manufacture of synthetic materials. The

manufacture of fibres, plastics, and synthetic intermediates frequently dictates that a specific aromatic hydrocarbon (free'of the isomers usually associated therewith) be employed as the initial raw material. The recovery of a single isomer of an aromatic hydrocarbon from its admixture with various other hydrocarbons including its isomers is an exceedingly difficult problem.

An object of this invention is to provide a method of treating hydrocarbon oils to remove undesirable components therefrom. Another object is to provide a methed for extracting aromatic hydrocarbons and sulfur compounds from hydrocarbon oils. A further object is to provide a process for the separation of polyalkyl benzenes according to their structural configuration. Numerous other objects and advantages of the present invention will be apparent from the detailed description thereof.

It has been discovered that polyalkyl benzenes, polynuclear aromatics and organic sulfur compounds can be extracted from hydrocarbon oils by the use of a solvent consisting of phosphoric acid having a certain P205-content and BFs employed in excess of a certain minimum amount. The phosphoric acid should have a P205 content between about 60 and 83% by weight, preferably between about 71 and 80% by weight. The BB: is

employed in excess of that amount which saturates the phoric acids.

phosphoric acid. This excess amount of ER; is at least one mole per mole of extractable component which is desired to be removed from the hydrocarbon oil undergoing treatment. The ER; is preferably employed in an amount sufiicient'to provide a partial pressure of BFs in the extraction zone of above about 50 p. s. i. g. usually about 50 to 3000 p. s. i. g. The phosphoric acid is employed in an amount at least sufiicient to form separate extract and rafiinate phases. The extraction may be carried out at a temperature between about 40 F. and 500 'F., preferably at a temperature below about 125 F. After thorough mixing of the phosphoric acid and BFa with the hydrocarbon oil, the rafiinate and heavier extract phases which are formed are separated. The raflinate and heavier extract phases are separated while in the presence of BFs in an amount in excess of that required to saturate'the phosphoric acid. Components such as polyalkyl benzenes, polynuclear aromatics or sulfur compounds which have been extracted from the oil and are now contained in the extract phase are separated therefrom.

It 'has also been found that the extracted components can be separated from the extract phase by removing BFs therefrom. This may be done by reducing the pressure in the separated extract phase. If the phosphoric acid employed has a P205 content of about 71 to weight per cent, reducing the pressure in the separated extract phase to atmospheric pressure will flash off BFs and spring extracted components from our solvent. The lighter-extracted components can then be removed from the heavier acid layer and the latter recycled to the extraction process together with the recovered BFa. When the phosphoric acid employed has less than about 71% or greater than 80% by weight of P205, it is usually necessary to resort to other techniques of separating extracted components from the extract phase. For example, the extract phase may be subjected to conditions of elevated temperatures and sub-atmospheric pressures to remove BFa and spring extracted components therefrom; Alternatively the extract phase may be diluted With water to springextracted components. This latter method is not a preferred one.

We have also discovered that it is possible to separate polyalkyl benzenes from eachv other as well as from aliphatic and alicyclic hydrocarbons which may be contained in the oil. The separation of polyalkyl benzenes is based on their structural configuration. It depends to a great extent upon the number of alkyl suhstituents in the polyalkyl benzene molecule and the location of the alkyl substituents in the benzene ring.

Thephosphoric acid which is employed in our invention has a P205 content of between about 60 and 83% by weight. Expressed in another fashion, orthophosphoric acid having an H3PO4 content of about 85 to 115% by Weight is. used. This range of phosphoric acids includes, orthophosphoric, pyrophosphoric, and polyphos- Phosphoric acids containing more than by weightof ,H3PO4 :are believed to contain varying amounts of, orthophosphoric, pyrophosphoric, and various chain lengthpolyphosphoric acids. It appears that there is an equilibrium mixture of the many phosphoric acids which correspond to a given ratio of H20 to P205. It is preferred to employ a phosphoric acid which has a P205 content of at least about 71 weight per cent and preferably not higher than about 80 weight percent. As the P205 content of the phosphoric acid is increased, its viscosity increases. The phosphoric acids which have a P205 content higher than about 83 weight per cent'are extremely viscous. If the P205 content of the phosphoric acid is increased from about 83 to 89% by weight, the acid becomes exceedingly more viscous until it becomes a solid at about 89 weight per cent 205. which e pond t m taph sphortccacid... For:

tuitously, the introduction of BFa into the phosphoric acid reduces the viscosity of the latter. Because of the very diflicult'problems in physically handlinganiext-reme- 1y viscous selective solvent, it is -:preferred.-;to employ" a phosphoric acid which has a- P205 content-notihigher than: about 83 weightper cent preferably not. higher than about 80 weight per cent. It has also been noted that metaphosphoric acid isineffectivelas. a-selective solvent when employed with BFa.

It has been found that if thePzOs content of the phos: phoric acid is. as low as about 60% by-weightor. as high as about 85% by weight,,itis not possible to separate the extracted components from the extract :phase as easily as is the case when-employinga phosphoric'acid having 2. P205 content'betweenabout 71and 80% by weight. If the phosphoric acidhas between .about7l and 80 weight per cent P205, it is .possibleqto removeextracted components from the extract phase byreleasing the pressure on the extract phase to atmospheric pressure. BFs is flashed offand extractedcomponents are sprung from the extract phase. A layer of the lighter extracted components forms above-the heavier layer. of phosphoric acid containing BFa. If the phosphorioacid which is employed has a P205 content of 60%byweight or 83% by weight, then. releasing'the'pressure on the extract phase to-atmospheric pressure'causessome. BFa to flash off but does not cause the separation of extracted components from the extract phase.- With these acids it is necessary to employ other-methods (which will be discussed later) for separating extracted components from the extract phase.

Surprisingly, it has been found that related'phosphorus acids such as metaphosphorus acid, hypophosphorus'acid and phosphonic acids are ineffective as selective solvents when employed with the necessary amount of BFs. It has been found to be essential to employ phosphoric acids of the abovedefined. compositions.

The phosphoric acid should be employed in-an amount sufficient so that it forms a separate phase. The amount of phosphoric acid which may be employed will depend upon the amount of extractable components one. desires to remove from the hydrocarbon oil undergoing treatment. In general no more than one mole of extractable component is removed per each phosphorus. atom contained in the phosphoric acid which is employed; Thus one mole of orthophosphoric acid will remove a maximum of one mole of an extractable components One mole of pyrophosphoric acid will remove a maximum of two moles of extractable component. The amount. of phosphoric acid which is employed will thusv depend upon the amount of such components which it is-desiredto remove. The greater the-amount ofeacid whiclnisemployed, the larger is the amountof extractablev components which are extractedfrorn the oil. Approximately to 1000 volume per cent of phosphoric acid, based upon oilmay be employed. Usually about25 to 200 volume per centphosphoric acidbased on. oilis...satisfactory. At the higher ratios of phosphoric acid ,to oil the phosphoric acid has an enhanced selectivity for. the extractable components.

When BFs is passed into a phosphoric acid (having .a P205 content of about-60 to 83. weight per :cent.) ;the BE; continues, to be absorbed by'the acidnntil the acid is saturated therewith. British 45l,35.9.-discloses-that BFs may be passed into orthoor pyrophosphoric-acid at atemperature between 20 and 200 F. or-thereabouts, and at about atmospheric pressure to;saturate-the-acid. The amount of BFs necessary to saturate our defined phosphoric acidsis about 1 gram mole-of BFa-per the sum. of the gram atoms of phosphorus plusgthe gram moles of uncombined water contained in the phosphoric acid. HaP-Ot) is'employed, about 1.0 mole of BFs-is necessary to saturate each mole of the -HsPO4 sinceeach mole of For example, if orthophosphoricacid; (100%:

H containsone atom of phosphorus and no uncombined Water. If aqueous HaPOr e. g. concentrated H3PO4 is used, then it would be necessary to use about 2 moles of BFs to saturate each mole of the 85 concentrated H3PO4. If the phosphoric acid is more highly concentrated than H3PO4 (viz. has a P205 content of 72 to 83 weight per cent) the amount of 3P3 in the BFz-saturatedphosphoric acid will vary only slightly from about-41 to 43 weight per cent.

In practicing our invention,, we employ the'BFs-saturatedgphosphoflc acid together. with additional amounts of The-amountofBFa employed in excess of that required to saturate the. phosphoric acid; is at least 1 mole per mole of extractable component which it is desired to remove. from. they oil. While. we do not wish to be bound by any theory, it is our belief that a coordination compound or adduct hereinafter called a complex is formed which consists of the BFs-saturated phosphoric acid, the- BFa inexcess -of that required to saturate the phosphoric. acid, and the extractable component. This complex has been visualized as follows:

[Extractable component BFs] [P O F531 4 The. complexes which are formed with the various extractable. components, have varying degrees of stability. To increase the'arnount of complex formed, IE3 is employed .in an amount larger than would theoretically be necessaryto complexwith each mole of extractable component. The larger the amount of ER; which is used inourextraction process, the greater .is the amount of extractablecomponents which are extracted from the oil. In practicing; our invention the hydrocarbon oil is contacted with the -BFs-saturated phosphoric acid in the presence of excess BFs. This excess BFs which is employed inthe contacting zone is usually an amount sufficient to provide a-partial pressure of BFs in the contacting zone of-at least about 50 p. s. i. g. BFa partial pressures of 50 to 3000p. s. i. g. or higher may be employed. To obtain a high .degree of extraction of extractable components, a. BF3 partial pressure about 500 and 2000 p. s. i.,g. may be employed.

The contacting of the hydrocarbon oil with the phosphoricv acid and .BFs may be effected at any temperature providedthe oil and phosphoric acid are in the liquid phases The BFa-saturated phosphoric acid is liquid at tempcratureslower than 40 F. Although it is possible to. extract attemperatures below. about -40 F. (and even lowertemperatures are'included Withinthe scope of'our invention), it isnot usually practical to do so since the oil andphosphoric acid become exceedingly viscous. The contacting may be carried out at temperatures as high as 500 F. although temperatures below about- F. are preferred in order to avoid side reactions due-to the catalytic effects of our solvent. When referring .tothe. solvent. of this invention, it is to be understood to mean. the defined-phosphoric acids saturated withBFa plusqexcess BFa necessary to complex with the extractable components. In general the capacity of the solventfor extractable components decreases as the contacting-temperature is increased. We prefer to operate at temperatures of from about 50 to about 100 F.

The- .-hydrocarbon oil is contacted with our solvent for a tlm8 ,Sllfi lCl6flT.- for the solvent to extract extractable components 'from the oil. This time will vary dependent upontheetficiency of contacting or mixing, which in turn depends on factors such as temperature (poorer mixingis obtained at lower. temperatures due to increased viscosity)-and other variables. Generally the contacting or mixing. time may befrom Ste 60 minutes in each extraction stage. Contacttimes greater than 1 hour may beiemployed but usually produce no greater efficiency in extraction. A very long: contact time especially at a high' temperature may result in side reactions of the hydrocarbons dueto the catalytic activity of our solvent.

- Becausetof the high :viscosity of some hydrocarbon oils,

it may be desirable to carry out the contacting thereof with our solvent in the presence of an inert diluent. Reducing the viscosity of the oil improves the contacting efficiency in the contacting zone and enables a greater degree of extraction. In addition the rafiinate .phase of a lower viscosity hydrocarbon oil can be separated more cleanly and rapidly from the extract phase. The diluent should be substantially inert to the phosphoric acid and BFa. It should not be afiected by the catalytic action of our solvent. Additionally, the diluent should be readily separable by distillation from the hydrocarbon oil although in some instances, it may be desirable to leave the diluent in the refined oil. Suitable diluents are pentane, hexane, petroleum ether, cyclohexanes, benzenes, toluene, and various naphtha fractions low in extractable components. Materials such as heptane or octane may suitably be used when the contacting is carried out at about ambient temperatures.

After the hydrocarbon oil has been mixed with our solvent for a time sufficient for the acid to remove extractable components from the oil, the mixture is settled. The solvent containing extractable components settles from the lighter oil. The heavier extract phase is then separated from the lighter raffinate phase. It is highly important that the phases be separated while in the presence of or under the influence of BE; in excess of that necessary to saturate the phosphoric acid. The phases are preferably separated while under a partial pressure of BFs of above about 50 p. s. i. g., usually about 50 to 3000 p. s. i. g. Separation of the phases is usually carried out under the same partial pressure of BF: and at about the same temperatures as existed during the extraction step. If desired, the extract phase may be washed with non-extractable hydrocarbons which serve the function of stripping out components from the extract phase which are not so strongly absorbed therein. The hydrocarbon diluents discussed in the preceding paragraph may be used for this purpose. This washing or stripping of the extract phase improves the selectivity of our solvent extraction process.

After separation of the extract phase from the raflinate phase, the extract phase is treated to recover extractable components therefrom. If the phosphoric acid employed has a P205 content of between about 71 and 80% by weight, the extracted components can be sprung from the extract phase by reducing the partial pressure of BFa which exists therein. As the partial pressure is reduced by venting BFs from the separated extract phase, extracted components separate from the solvent. The less stable complexes formed between the extractable components and our selective solvent are the first to decompose. As the partial pressure of BE; in the separated extract phase is lowered, additional amounts of extracted components are sprung from the selective solvent and form a separate and lighter layer. It is readily apparent that the reduction of the partial pressure of BFs may be stopped at any point to control the amount of extractable components which are sprung from the extract phase. A number of fractions of oil having different characteristics may be separated from the extract phase by reducing the partial pressure of BFa, separating the extracted components which have been sprung, and repeating the cycle. During the springing step an inert hydrocarbon may be employed to wash the extract phase to insure the substantially complete removal of sprung hydrocarbons from the selective solvent. The BF3 may be rapidly removed from the extract phase at the temperature employed in the extraction step and generally at a somewhat higher temperature. Thus, while BFs may be removed from the extract phase at temperatures as high as 500 F. (cracking and other reactions of the extracted components may occur at this high temperature), it is preferred to effect flashing of the BFs from the extract phase at a temperature below about 200 F. The BF; which is thus flashed from the separated extract 'a suitable feed to the. process.

phase, may be recycled for further use in the extraction step. Likewise the phosphoric acid layer may be recycled. It is of course necessary to separate extracted components from the fully saturated selective solvent before reusing for further extraction, otherwise no additional extraction will occur.

If the phosphoric acid employed has a P205 content greater than about 180% or less than about 71% by weight, the extracted .components are not separated from the extract phase merely by reducing the partial pressure of BFs to atmospheric. Although BFz is thereby flashed off, extracted components are not sprung. By subjecting the separated extract phase (after reducing its pressure to atmospheric) to an elevated temperature e. g. as high as 200 to 300 F. and a reduced pressure e. g. as low as 50 to 200 mm. abs., extracted components are sprung from the extract. Thus vacuum distillation can be used to separate extracted components from the extract phase. If desired the extracted components can be sprung from the separated extract phase by treatment thereof with water, preferably cold water or ice. The upper layer of extracted components can then be separated from the lower aqueous layer. It is readily apparent that the use of the preferred phosphoric acid, viz. 71 to wt. per cent P205, has very great advantage in the step of recovering extracted components from the extract phase. The solvent can easily be recovered and reused. The water .dilution technique in effect destroys the solvent for further use.

The feed to our process may be a hydrocarbon oil which contains extractable components. Polyalkylbenzenes, polynuclear aromatics and organic sulfur compounds and the like can be removed selectively from the oil by the process of our invention. Any of a wide variety of hydrocarbon oils can be charged to the extraction zone. Various fractions obtained from the distillation of petroleum, for example, naphthas, kerosenes, heater oil, lube oils, etc. or the crude oil itself, may be used as the feed stock. Hydrocarbon oil derived from the treatment of the above materials, for example, naphthas. obtained from catalytic cracking or hydrc forming or rafiinates or extracts from the solvent refining of naphthas or kerosenes, may be employed as the feed oil. The boiling point of the hydrocarbon oil charged is of no especial consequence so long as it contains extractable components. Suitably it may be between about 200 and 750 F. .Shale oil and its various fractions are The so-called light oil from the coking of a coal may also be employed. The liquid products produced during the hydrogenation of coal may be employed as a charging stock to our process.

The rafiinate from our process will usually be the desired product because of its reduced sulfur content and its reduced aromatic content. This is usually the case when the charging stock is a lube oil stock, a kerosene or a high sulfur stock which it is desired to desulfuri'ze. Cycle gas oils are also extracted by our process to produce a rafiinate of reduced sulfur and aromatic content which is an excellent stock for recycling to catalytic cracking.

It may be desirable to extract hydrocarbon oils for the purpose of recovering aromatic hydrocarbons from the oil. Thus, the extracted components rather than the rafi-lnate oil may be the desired fraction. It is possible by our invention to extract polyalkyl benzenes from other close boiling hydrocarbons. Thus an extract oil rich in polyalkyl' benzenes may be recovered and employed as high anti-knock engine fuel. Our solvent does not seem to complex with benzene or toluene alone. If there are extractable components in the feed e. g. polyalkylbenzenes, then benzene and/or toluene are dissolved in the extract phase in larger amounts. The presence of complexed components improves their solubility.

We have also discovered that polyalkylbenzenes can be separated from each other as well as from aliphatic and valicyclic hydrocarbons. The separation of polyalkyibenzenes depends upon their structural configuraform complexes with the solvent which are more stable than those formed from polyalkylbenzenes having the same number of alkyl substituents but substituted in different positions in the benzene ring. The stability of the complex of a polyalkyl benzene with phosphoric acid and BF3 is reflected by the pressure at which it dissociates. The higher its dissociation pressure, the less stable is the complex. If the extraction of the polyalkylbenzenes and the separation of the extract phase are both carried out at a pressure above the dissociation pressure of a complex of a specific polyalkylbenzene with phosphoric acid and BF3, but at lesser partial pressure of BFs than the dissociation pressure of a complex of a different polyalkylbenzene with phosphoric acid and BFs, a separation between the two polyalkylbenzenes can be made. By taking advantage of the differing stabilities of the complexes of various polyalkyl benzenes with phosphoric acid and BFs, a number of separations between polyalkylbenzenes can be effected. 1,3-dialkyl benzenes can be separated from dialkyl benzenes having their alkyl substituents in other positions in the benzene ring. Similarly 1,3,5-trialkyl benzenes can be separated from trialkyl benzenes having alkyl substituents in other positions in the benzene ring. In addition 1,3,5-trialkyl benzenes can be separated from any of the dialkyl benzenes. Also l,2,3,5-tetra-alkyl benzene can be separated from any dialkyl or trialkyl benzenes and from isomeric tetra-alkyl benzenes. Penta-alkyl benzene can be separated from any polyalkyl benzene having a lesser number of alkyl substitutents in the benzene ring, and hexa-alkyl benzene is separable in an analogous manner from polyalkyl benzenes having a lesser number of alkyl substituents.

In another modification of our extraction process, substantially all of the polyalkyl benzenes (or whatever portion of the polyalkylbenzenes is desired) can be extracted from the hydrocarbon oil. After separating the extract phase the BF; pressure thereon may be partially released to spring or form an additional raffinate phase. The raffinate phase will contain polyalkylbenzenes whose complexes with our solvent are less stable at lower BF3 partial pressures. For example, highly aromatic naphtha fractions such as the product of hydroforming may be extracted with our solvent under BF3 partial pressures of 2000 p. s. i. g. or higher to produce an extract phase containing substantially all of the polyalkyl benzenes contained in the hydroformate. The partial pressure of 8P3 existent in the separated extract phase is then reduced to about 500 p. s. i. g. whereupon a lighter raffinate layer is formed. The rafiinate layer is rich in dialkyl and other more completely substituted polyalkyl benzenes which are not substituted in the 1,3,5-positions. The extract is rich in polyalkyl benzenes substituted in the 1,3,5-positions including triand higher polyalkyl benzenes. Thus substantially complete separation of polyalkyl benzenes may be made from a hydrocarbon oil and the polyalkyl benzenes may subsequently be separated into fractions which are enriched in diifering polyalkyl benzenes.

Our solvent also has catalytic activity for causing the shifting of alkyl groups on alkyl benzenes. The more highly branched alkyl substituents are more mobile. This mobility, which is reflected by the extent of conversion of the alkylbenzenes, increases with temperature, thoroughness of mixing, contact time, ratio of phosphoric acid to alkylbenzene, and increasing chain length of the alkyl substituents in the alkyl benzene. When the alkyl substituent contains more than about 4 carbon atoms, there is a tendency for the side chain to isomerize and even crack. Isopropyl, sec-butyl, and tert-butyl side chains become highly mobile at about 70 F. Temperatures in the neighborhood of 85 or 100 F. are necessary before ethyl side chains become highly mobile. An even higher temperature viz. around 125 1?. is needed in order to render methyl side chains highly mobile.

It has been found that our solvent-catalyst is capable of rapidly disproportionating alkyl benzene. When our solvent-catalyst is employed (preferably under a BF: partial pressure of p. s. i. g. or higher) at a temperature of 0 to 200 F., alkyl benzene may be disproportionated to produce the symmetrical 1,3,5-trialkylbenzene in a large proportion. A temperature below 200 F. is preferred in the contacting step to minimize the formation of other isomeric trialkyl benzenes. The phosphoric acid is employed in an amount of from 0.25 to 10, preferably about 3 volumes per volume of alkyl benzene feed. A contact time of from 0.25 to 10 hours, suitably about 2 to 6 hours may be employed. For example, ethylbenzene may be contacted with about 3 volumes of pyrophosphoric acid under a BFz partial pressure of 500 p. s. i. g. for about 4 hours at about 200 F. to produce 1,3,5-triethylbenzene in large amounts. The production of diethylbenzene is negligible.

It has also been discovered that polyalkyl benzenes such as trialkyl benzene and tetra-alkyl benzene can be isomerized to produce polyalkyl benzene having a high concentration of those polyalkyl benzenes which have alkyl substitutents in the 1,3,5-positions in the benzene ring. Our solvent-catalyst is used at a SP3 partial pressure of about 100 p. s. i. g. or higher. Reaction temperatures of 0 to 200 F. may be employed. A temperature higher than 200 F. causes the formation of larger amounts of polyalkyl benzenes having alkyl substituents other than in the 1,3,5-positions. In general the tetraalkyl benzenes require somewhat higher temperatures to effect isomerization than do the trialkyl benzenes. The phosphoric acid is employed in an amount of from 0.25 to 10, preferably about 3 volumes per volume of alkyl benzene feed. Contact times of 0.25 to 10 hours or more, preferably about 2 to 6 hours may be used. For example, trimethyl benzenes may be isomerized to 1,3,5- trirnethyl-benzene by contacting the feed with about 3 volumes of pyrophosphoric acid under a BFs partial pressure of about 500 p. s. i. g. at a temperature of about F. for about 4 hours.

We have also discovered that'if ethylbenzene and metaxylene plus orthoxylene or paraxylene are contacted with our solvent-catalyst, it is possible to produce a xylene fraction which is enriched in the xylene isomers other than metaxylene and an ethylxylene fraction rich in the 1,3,S-isomer. The reaction effect is carried out preferably at a temperature of about 70 to 125 F. although a temperature as low as 0 F. and as high as about'200 F. may be employed. Our solvent-catalyst is employed while using a BF3 partial pressure of 100 p. s. i. g. or higher, suitably 2000 p. s. i. g. While the volumetric ratio of phosphoric acid to alkyl benzene feed may vary from 0.25 to 10:1, a preferred ratio is about 3:1. A reaction time of 1 to 10 or more hours, preferably about 4 to 8 hours is employed. The extract phase recovered is rich in ethylxylene and the raftinate phase is rich in xylenes other than meta-xylene. In a process modification, the reaction is carried out in two stages. A short contact time e. g. l to 2 hours, is used in the first step, following which a phase separation is made. The rafiinate phase is enriched in xylene isomers other than metaxylene. The extract phase is reacted for an additional length of time e. g. l to 10 hours, to produce a high yield of 1,3,5-ethylxylene. After the reaction has been completed, the products may then be recovered by removing BFs from the reaction product and separating the hydrocarbon layer from the phosphoric acid layer. Alter natively, the products may be recovered after the reaction has been completed by separating an extract phase rich in 1,3,5-ethylxylene from the rafiinate phase which contains large amounts of benzene and ethylbenzene.

y We have also found that mononuclear aromaticscan be alkylated with olefins containing 2 to 4 carbon atoms to produce polyalkyl benzenes having alkylsubstituents in the 1,3,5-positions in the benzene ring. The alkylation may be carried out at a temperature of to 200 F., the higher molecular weight olefin being employed at the lower temperatures. A temperature of'about 70 F. is used when propylenes or butylenesare employed and a temperature of about 100 F. is employed when ethylene is used. The BFs is employed in our solventcatalyst in amounts to provide a partial pressure of BFs higher than about 100 p. s. i. g. The phosphoric acid to hydrocarbon volumetric ratio may be from 0.25 to 10:1 e. g. 3:1. To prepare the 1,3,5-trialkylbenzene, at least the stoichiometric amount of necessary'olefins should be introduced. The olefin should be introduced slowly e. g. over a period of 0.5 to 10 hours or more. For example, meta-xylene may be alkylated with ethylene to produce 1,3,5-ethy1xylene. Benzene may be converted in a very large proportion to 1,3,5-triethylbenzene by contacting benzene with about three moles of ethylene and about three volumes of pyrophosphoric acid under a BFs partial pressure of 500 p. s. i. g. and a temperature of about 75 F. for four hours.

A number of experiments were performed which demonstrate the effectiveness of our invention. The procedure which was followed in the experiments was as follows: The feed oil was charged to a Hastelloy autoclave of 250 cc. capacity. The phosphoric acid saturated with BFs was then added to the autoclave. The BF:- saturated phosphoric acid was prepared by passing BF: at room temperature into the particular phosphoric acid employed and at about atmospheric pressure until no change in weight of the phosphoric acid was observed. The autoclave was then pressured with BFs to the partial pressure of 3P3 which was desired. In some experiments the phosphoric acid was saturated with BF after introduction into the autoclave. The contentswere then mixed for the desired length of time which was usually between /2 and 8 hours depending on the elfectiveness of mixing. The contents of the autoclave were then settled for about 1 hour. The heavier extract layer was then withdrawn from the autoclave while maintaining the partial pressure of BFs within the autoclave. The raffinate layer was then recovered. The BFz pressure on the separated extract phase was then released and BE; flashed into a liquid nitrogen trap for recovery. From the extract phase, now at about atmospheric pressure, were recovered the extracted components. In certain instances the extracted components were recovered by decantation of the separate layer which formed above the acid layer. In other experiments, depending upon the P20 content of the phosphoric acid employed, the extract phase was diluted with water at Dry Ice temperatures to spring the extracted components from the extract phase.

The first series of experiments demonstrate the effectiveness of our invention in reducing the sulfur content and the aromatic content of hydrocarbon oils. The hydrocarbon oil employed in run No. 1 was a heavy catalytic cycle gas oil. A West Texas virgin gas oil was employed in run No. 2. The feed to run No. 3 consisted of 4.04 volume per cent diphenyl sulfide in n-heptane. The gas oils which were employed had the following inspections:

In extracting the above feed stocks, approximately 100 cc. of feed was contacted with 20 cc. of phosphoric acid, the P205 content of the phosphoric acid being about 82 weight per cent. A temperature of about 75 to F. and a BF3 partial pressure of 500 p. s. i. g. were maintained within the autoclave. The contents were mixed for about 2 hours and then settled for one hour to effect stratification. After separation of the heavier extract phase and release of BF pressure therefrom, the extract was diluted with water at Dry Ice temperatures to spring the extracted components. The extent of desulfurization and dearomatization of the raffinate oils were then determined. The treating loss as measured by the volume of oil lost to the extract phase was measured. The results obtainedare shown in Table I which follows:

The excellent desulfurizationability of our solvent is readily apparent. It is particularly noticeable from run No. 3 where a desulfurization of 94% was attained. The treating loss in run No. 3 was only 4% which corresponds approximately with the 4.04 volume per cent of organic sulfur compound in the feed. The high selectivity of our solvent for organic sulfur compounds makes it very useful in petroleum refining. The ability to remove aromatic hydrocarbons from the charging stock as evidenced by the results of runs No. 1 and 2 makes our process useful in producing a rafiinate oil which is an improved charging stock to catalytic cracking for the production of gasoline.

The value of our process in improving the quality of lubricating oil stocks has also been demonstrated. It has been shown that our process is capable of improving the viscosity index by a very considerable amount. In run No. 4 a 20W base stock having a gravity 01322.5 API, a viscosity at F. of 311.4 SSU, a viscosity index of 50, a sulfur content of 1.61 weight per cent, and an NPA color of 3 was extracted with our selective solvent under conditions identical with those discussed in the preceding desulfurization and dearomatization experiments. About 69% of the oil was recovered as a raflinate oil (31 volume per cent treating loss). This oil hard a viscosity at 100 F. of 201.2 SSU, a viscosity index of 78, a sulfur content of 0.43 weight per cent (which corresponds to a desulfurization of 81.6%) and was water-white in color. Thus our invention is applicable to the extraction of lube oil stocks to improve viscosity index, lower the sulfur content, and improve the color.

An additional series of runs were conducted which demonstrate the eflect of the P205 content of the phosphoric acid on the manner in which the extracted components can be recovered from the extract phase. The feed employed was 33 volume per cent mesitylene in nheptane. Phosphoric acids (50cc. in each run) of dif fering P205 contents were used in each run. Hydrocarbon feed was also employed in the amount of 50 cc. per run. The extraction was conducted at a temperature of about 75 to 80 F. and under a partial pressure of BFa of 500 p. s. i. g. The contents of the autoclave were mixed for about 30 minutes and then settled for about 30 minutes. The extract phase was withdrawn from the autoclave while under the stated partial pressure of BFs. The extracted components were then recovered from the 1-1 separated extractaphase. The results obtained are shown in TablelI whichifollowsz v It'is'i'mportant to note-from Tablc II'that when thePzOs content'of the phosphoric acid was 61.6 wt. per cent (corresponding to 86% concentrated 11131- 04), the extracted mesitylene could not be separated from the extract phase by depressuring the extract phase to atmospheric pressure to remove BFa. No separation of mesitylene was observed even though the extract phase was allowed to stand for l2hours. However, when the phos pho'ric acid employed had a P205 content of 72.4 or 78.9 .weightpercent, the extracted mesitylenecouldbe recovered from the separated extract phase merely by reducing the pressure on the extract phase to atmospheric pressure. The BFa was flashed E and a supernatant layer of mesitylene was formed above the acid layer. Themesitylene was then recovered by decantation. In additional experiments it has been shown that if an extract suchas isobtained from run No. 5 is depressured to atmospheric conditions and then heated to about 130 Fl, while reducing the absolute pressure to 200 mm., some extracted oil separates from the extract phase and can be recovered by decantation.

'Theimportance of employing BFs in excess of the amountnecesasry to saturate the phosphoric acid has i been demonstrated in a number of experiments. These experiments also demonstrate the efiectiveness of our selective solvent for separating one polyalkyl benzene from adifierent polyalkyl benzene. The feed to each .run was 50 cc. of an equal volume mixture of mesitylene, mxylene, andn-heptane. The extraction was conducted at a temperature of about 75F. and under a partial pressure of BFs which diflfered in each run and w-asin the range of 8p. s. i. g. to 550 p. s.. i. g. The phosphoric a'cidcmployed had a P205 content of 582% by .weight. hi each run, including run No..8 which was the first run, 50: cc.. 'ofiiBFsasaturate'd phosphoric acid which had previously'been used inextracting mesitylene was em- .ployed.. Therreaction mixture was agitated .forabout -1 to.2.-hours andithen settled for anequivalentlength'of time. Theextract phase was. separated Whilesubjected to the samepartial pressure of --BF3 as was employed duringthe extraction operation. The pressure on the extract. phase .was' then reduced to atmospheric A pressure whereupon extracted components were sprung from the extract-alayer. Analyses of the sprungextract oil and the raflinate oilwere then-made. The results obtained .are shown in Table III which follows:

. (Cone. ME) (Cone. X

1 r n a L S i lstrihutron coefhcient lb (301391 In) (3on0. XE) where M stand for mesitylcne, X stands for iii-xylene, and subscripts E and R stand for extract and rafilnate respectively.

the extraction under a readily. apparent from graphically illustrated (Fhe importance .of conducting positive partial: pressure I of BFat is the .-ab,ove data. These data are in Figure 1.

by way of line A preferred embodiment of our invention will be described with relation 'to Figure 2 which is a schematic representation of an adaptation of our process for extracting mesitylene from'afraction of'hydroformed naphtha. alves, pumps and the'like have been omitted from the flowdiagram of Figure 2 for purposes of clarity.

Phosphoric acid having a P205 content of 78 weight per cent is'introduced from source 11 by way of valved line 12 into vessel 13 which is capable of withstanding high pressures. Anhydrous BFa is passed from source 14 by way of valved line 16 into vessel 13. Because saturation of the phosphoric acid with BFs is an exothermic reaction, vessel 13 is provided with cooling means 17 to maintain the temperature at .not higher than about :F. The BFs is introduced into vessel 13 so that a partial pressure of BFaOf about p. s. i. g. is maintained therein. The solvent (which consists of BFasaturated phosphoric acidand BFa in partial pressure of 100 p. s. -i. g.) is passed by way of valved line 18 into the extractor- 19 at a-point near its top.

Becauseour solvent is'corrosive to ordinary metals, it is'usually necessary to employ somematerial of construction which is not effected by the solvent. Aluminum and Hastelloyhave been found to be outstanding with regard to resistance to. corrosion by our selective solvent.

Extractor 19 is.-a single-stage countercurrent extraction column. Thehydrocarbonfeed is passed from source 21 by way of valved line 22 into extractor 19 at a point not far above its bottom. The hydrocarbon feed employed is a fraction of hydroformed naphtha which boilsbetween about 270 and400 F. It contains a substantial amount of trimethyl benzenes including mesitylene, other alkylatedaromatic hydrocarbons, and associated aliphatic and alicyclic hydrocarbons. The selective solvent is thoroughly mixed with the hydrocarbon feed at a temperature of about 75 F. for about 15 minutes. Approximately 0.5 liquid volume :of our-selective solvent is introduced per volume of hydrocarbon feed. The BF partial pressure is maintained at about 100 p. s. i. g. within extractor 19 by introducing BFa at vertically spaced points in the reactor through a manifolding system represented by valvedllines 23, 23a, and 23b. The extract phase which at thebottom of extractor 19 is countcrcurrently washed with heptane. 'Heptane is introduced from source 24 by way of valved line 26 into extractor 19 at a point below the hydrocarbon feed inlet'22 and above the withdrawal line 27 by which the extract phase is removed. About 0.2 volume of heptane is employed per volurneof hydrocarbon feed.

The extract phase is removed from extractor 19 while under a BF; partialpressure of 100 p. s. i. g. and passed byway of line 27 to heater 28. The extract phase is heatedtoabout 100 F. and then passed by way of line 29 into extract decomposer 31. In decomposer 31 the pressure onthe extract phase is reduced to atmospheric pressure which causes-BFa to flash from the extract phase. The flashed BF; is' removed from decomposer 31 and recycled by way of line'32 either to extractor 1901? into valved line 16 forforming fresh solvent in vessel 13. The liquidextract phase remaining in decomposer 31 is passed by way of line 33 into settler 34. The heavier acid layer is-removed frornsettler 34 and passed by way of line 36 into valved line 12 whereby it is recycled to vessel 13 for the formation of further amounts of selective solvent. The lighter hydrocarbon layer is removed from settler 3'4 and passed by way of line 37 into coalescer 3S.

Coalescer 38 maybe a rock salt coalescer or other means effective for removing residual amounts of acid from the oil. The recovered acid is removed-from coalescer 35 39. If desired it may be reused for-the extraction of additional amounts of hydrocarbon feed. The extracted oil is removed from coalescer 38 and passed byway ofline'41 into fractionator 42. Here the residual amounts of BFs and other low-boiling components including any xylenes present are distilled over- 13 head. A bottoms fraction containing high boiling materials such as tetramethylbenzenes, ethyltrimethylbenzenes, and the like, is removed. A side-cut consisting of about 95% purity mesi-tylene is recovered and passed by way of line 43 to storage, not shown. The rafiinate phase is removed from extractor 19 and passed by way of line 44 to means for recovering heptane and railinate oil. The heptane may be recycled to the extractor. The ratfinate oil may be neutralized and washed prior to sending to storage.

Thus having described our invention what is claimed is:

1. A process of treating a hydrocarbon oil to separate an extractable component selected from the class consisting of polyalkyl benzenes, polynuclear aromatics, and organic sulfur compounds which process comprises contacting in a contacting zone at a temperature below about 125 F. said hydrocarbon oil containing at least one of said extractable components with about to 1000 volume percent based on said oil of a phosphoric acid having a P205 content between about 71 and 80% by weight and BF3 in an amount suflicient to provide a partial pressure thereof in the contacting zone of between about 50 and 3000 p. s. i. g., forming a rafiinate phase and a heavier extract phase, separating said phases while under said partial pressure of BF; into a rafiinate phase and a heavier extract phase containing extractable components, and removing extracted components from said extract phase.

2. The process of claim 1 wherein said contacting is carried out in the presence of a hydrocarbon diluent that is substantially inert to the action of the phosphoric acid and BF3.

3. The process of claim 1 wherein ER; is released from the separated extract phase to separate extracted components therefrom.

4. The process of claim 3 wherein said extractable component is an organic sulfur compound.

5. The process of claim 1 wherein said hydrocarbon oil is a lubricating oil stock.

6. The process of claim 1 wherein said extractable component is a polyalkyl benzene.

7. The process of claim 1 wherein said hydrocarbon oil contains a mixture of polyalkyl benzenes and wherein only a portion of said polyalkyl benzenes are extracted in said extract phase, the remainder of said polyalkyl benzenes being contained in said rafiinate phase.

8. The process of claim 1 wherein said hydrocarbon oil is a petroleum fraction boiling within the range of about 270 and 400 F. which contains trialkyl benzenes, wherein a polyalkyl benzene substituted in the 1,3,5- positions with alkyl groups is recovered from said extract phase.

9. A process of treating a hydrocarbon oil to separate an extractable component selected from the class consisting of polyalkylbenzenes, polynuclear aromatics and organic sulfur compounds which process comprises contacting said hydrocarbon oil containing at least one of said extractable components with phosphoric acid having a P203 content between about 60 and 83% by weight and BF3, said phosphoric acid being employed in an amount in excess of its solubility in said hydrocarbon oil, carrying out said contacting at a temperature below about 500 F. and under a partial pressure of BF in excess of about p. s. i. g., forming a rafiinate phase and a heavier extract phase containing extractable components, separating said phases, and removing extracted components from said extract phase.

10. A process of treating a hydrocarbon oil to separate an extractable component selected from the class consisting of polyalkylbenzenes, polynuclear aromatics, and organic sulfur compounds which process comprises contacting at a temperature below about 500 F. said hydrocarbon oil containing at least one of said extractable components with phosphoric acid having a P205 content between about and 83% by weight and BF3, said phosphoric acid being employed in an amount of about 5 to 1000 volume percent based on said oil, carrying out said contacting under a partial pressure of BF3 of between about 50 and 3000 p. s. i. g., forming a rafiinate phase and a heavier extract phase containing extractable components, separating said phases while subject to said BFa partial pressure, and removing extracted components from said extract phase.

References Cited in the file of this patent UNITED STATES PATENTS 1,092,448 Melamid Apr. 7, 1914 2,174,908 Ault et a1. Oct. 3, 1939 2,308,001 Forney Jan. 12, 1943 2,495,851 Lien et al. Jan. 31, 1950 2,671,047 Arnold et a1. Mar. 2, 1954 

1. A PROCESS OF TREATING A HYDROCARBON OIL TO SEPARATE AN EXTRACTABLE COMPONENT SELECTED FROM THE CLASS CONSISTING OF POLYALKYL BENZENES, POLYNUCLEAR AROMATICS, AND ORGANIC SULFUR COMPOUNDS WHICH PROCESS COMPRISES CONTACTING IN A CONTACTING ZONE AT A TEMPERATURE BELOW ABOUT 125* F. SAID HYDROCARBON OIL CONTAINING AT LEAST ONE OF SAID EXTRACTABLE COMPONENTS WITH ABOUT 5 TO 1000 VOLUME PERCENT BASED ON SAID OIL OF A PHOSPHORIC ACID HAVING A P2O5 CONTENT BETWEEN ABOUT 71 AND 80% BY WEIGHT AND BF3 IN AN AMOUNT SUFFICIENT OT PROVIDE A PARTIAL PRESSURE THEREOF IN THE CONTACTING ZONE OF BETWEEN ABOUT 50 AND 3000 P.S.I.G., FORMING A RAFFINATE PHASE AND A HEAVIER EXTRACT PHASE, SEPARATING SAID PHASES WHILE UNDER SAID PARTIAL PRESSURE OF BF3 INTO A RAFFINATE PHASE AND A HEAVIER EXTRACT PHASE CONTAINING EXTRACTABLE COMPONENTS, AND REMOVING EXTRACTED COMPONENTS FROM SAID EXTRACT PHASE. 